QPix Technology: Research and Development towards kiloTon scale - - PowerPoint PPT Presentation

QPix Technology: Research and Development towards kiloTon scale pixelated LArTPC

Jonathan Asaadi University of Texas at Arlington

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Work based on original paper by Dave Nygren (UTA) and Yuan Mei (LBNL): arXiv:1809.10213

Introduction

• Liquid Argon Time Projection Chambers (LArTPC’s) offer access to

very high quality and detailed information

• Leveraging this information allows unprecedented access to detailed

neutrino interaction specifics from MeV - GeV scales

• Capturing this data w/o compromise and maintaining the intrinsic 3-D

quality is an essential component of all LArTPC readouts!

2 Credit: arxiv: 1903.05663

2D-Projective Readout 3D-Pixel Readout

Introduction

• Conventional LArTPC’s use sets of

wire planes at different orientations to reconstruct the 3D image

○ Challenge in reconstruction of complex topologies

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• Being able to readout using pixels instead of wires

could off a solution

○ “Cost” of many more channels! 2 meter x 2 meter readout ■ 3mm wire pitch w/ three planes = 2450 channels ■ 3mm pixel pitch = 422,000 channels

• Requires an “unorthodox” solution
• kiloTon scale LArTPC’s use “wrapped wire” geometries

to reduce the number of readout channels

○ Challenging to engineer such massive structures

Introduction

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• Simulation studies comparing the

readout of 2D projective LArTPC’s to 3D pixel LArTPC’s shows that 3D based readout offers significant improvement in all physics categories!

○ 𝝃e-CC inclusive: 17% gain in efficiency and 12 % gain in purity ○ 𝝃𝜈-CC inclusive: 10% gain in efficiency for 99% purity ○ NC𝜌0: 13% gain in efficiency and 6% gain in purity ○ Also offers gains in Neutrino-ID classification and final state topology ID

4mm x 4mm 3d voxels

𝝃e-CC simulated event *** Improvements like these can lead to significantly shorter experimental running time required to meet desired physics goals! paper in preparation (additional details in backup) slides

Introduction

• Kiloton scale LArTPC’s (such as DUNE) afford a

huge “big data” challenge to extract all the details

• ffered by LArTPC

○ 1 second of DUNE full stream data ~4.6 TB (for 1.5 million channels)

■ 1 year of full stream data ~ 145 EB (exabytes)

• However, most of the time there is “nothing of

interest” going on in the detector

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○ But you must be ready “instantly” when something happens (proton decay, supernova, beam event, etc)

• To readout such massive detectors with pixels requires an enormous

number of channels

○ 𝓟 (130 million) per 10 kTon at 4mm pitch ○ Requires an “unorthodox” solution

An “unorthodox” solution

• The Q-Pix pixel readout follows the “electronic principle of

least action”

○ Don’t do anything unless there is something to do ■ Offers a solution to the immense data rates

• Quiescent data rate 𝓟(50 Mb/s)

■ Allows for the pixelization of massive detectors

• Q-Pix offers an innovation in signal capture with a new

approach and measures time-to-charge:(ΔQ)

○ Keeps the detailed waveforms of the LArTPC ○ Attempts to exploit 39Ar to provide an automatic charge calibration

• “Novelty does not automatically confer benefit”

○ Much remains to be explored

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Q-Pix: The Charge Integrate-Reset (CIR) Block

• Charge from a pixel (In) integrates on a charge sensitive

amplifier (A) until a threshold (Vth~ΔQ/Cf) is met which fires the Schmitt Trigger which causes a reset (Mf) and the loop repeats

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“reset” switch Charge sensitive Amp. Schmitt Trigger

• Measure the time of the “reset” using a local clock (within

the ASIC)

• Basic datum is 64 bits

○ 32 bit time + pixel address + ASIC ID + Configuration + ...

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Q-Pix: The Charge Integrate-Reset (CIR) Block

What is new here?

• Take the difference between sequential resets

○ Reset Time Difference = RTD

• Total charge for any RTD = ΔQ
• RTD’s measure the instantaneous current and captures

the waveform

○ Small average current (background) = Large RTD ■ Background from 39Ar ~ 100 aA ○ Large average current (signal) = Small RTD ■ Typical minimum ionizing track ~ 1.5 nA

• Signal / Background ~ 107

○ Background and Signal should be easy to distinguish ○ No signal differentiation (unlike induction wires)

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Reset Time Difference

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ΔQ~1.0 fC (~6000 e-)

Nygren & Mei arXiv:1809.10213

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ΔQ~0.3 fC (~1800 e-)

Nygren & Mei arXiv:1809.10213

How the time stamping works

• One free running clock per ASIC (50-100 MHz)

○ Required precision for DUNE δf/f ~10-6 per second

■ Expect this to be easily achieved in liquid argon

• Time stamping routine has the ASIC asked once per

second “what time is it?”

○ ASIC captures local time and sends it ○ Simple linear transformation to master clock synced to GMT ○ RTD’s calculated “off chip”

• Has this idea been realized before?

○ YES! In ICECUBE (by Nygren)

■ Oscillator precision achieved > 10-10 /s (hard to measure)

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Q-Pix ASIC Concept

• 16-32 pixels / ASIC

○ 1 Free-running clock/ASIC ○ 1 capture register for clock value, ASIC, pixel subset ○ Necessary buffer depth for beam/burst events ○ State machine to manage dynamic network, token passing, clock domain crossing, data transfer to network (many details to be worked out)

• Basic unit would be a “tile” of 16x16

ASICs (4092 4mm x 4mm pixels)

○ Tile size 25.6 cm x 25.6 cm

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Q-Pix Consortium

• A consortium of universities and labs has

formed to realize the Q-Pix concept

○ Done in close collaboration with LArPix (JINST 13 P10007) readout for the DUNE near detector

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• Four central ideas being worked on

○ Physics Simulations: Quantify the conferred benefit

• f pixel vs. wire readout and the requirements of

the ASIC design ○ CIR Input: all extraneous leakage current at the input node needs to be small (aA) ○ Clock: δf/f ~10-6 per second ○ Light Detection: Exploring new ideas using photoconductors on the surface of the pixels (see the next talk from E. Gramellini)

Physics Simulation

• To quantify the range of currents the Q-Pix ASIC will see we are using

simulations of neutrino interactions in argon

• We can take the charge seen by a pixel and translate this into current

as a function of time

• We can then use this simulation to set the physics requirements on

the Q-Pix ASIC ○ Allowed reset time, minimum ΔQ, etc…

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Charge seen by single pixel near the vertex

Convert to Current

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Physics Simulation

• Measurement of Longitudinal Diffusion

○ Using a small sample muons a novel technique in Q-Pix can be seen

Calculation from: https://arxiv.org/pdf/1508.07059.pdf

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Physics Simulation

• Measurement of Longitudinal

Diffusion ○ The average RTD versus the drift length carries the diffusion information

• Allows for a fundamental

measurement with few statistics

• DL

Measured = 6.47土0.97 cm2/s

○ DL

Simulation = 6.82 cm2/s

Conclusions

• Readout requirements for kiloton scale LArTPC’s offer many

challenges to fully exploit the rich data they have to offer ○ We must optimize for discovery!!!

• Low threshold pixel based readout can optimize for discovery

the impact of these detectors ○ Requires an unorthodox solution

• The Q-Pix concept may afford a way to pixelize a kiloton scale

LArTPC and retain all the details of data ○ The devil lives in the details, but an effort is underway with promising preliminary results ○ Stay tuned for more updates!

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Q-Pix consortium would like the thank the DOE for its support via DE-SC0020065 award

Backup Slides

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Q-Pix consortium would like the thank the DOE for its support via DE-SC0020065 award

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Intrinsic reconstruction pathologies associated with charge deposited along the direction of the wires

Introduction

Introduction

• Liquid Argon Time Projection

Chambers (LArTPC’s) offer access to very high quality and detailed information

• Leveraging this information allows

unprecedented access to detailed neutrino interaction specifics from MeV - GeV scales

• Capturing this data w/o

compromise and maintaining the intrinsic 3-D quality is an essential component of all LArTPC readouts!

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Wire Number Drift Time ArgoNeuT Data CC-0𝜌 w/ photon activity

Candidate one-track NC 𝜌0 event from MicroBooNE Run 1 BNB data

Light Detection

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• One very “blue sky” idea currently

being considered is to see if the same pixels which collect ionization charge can be used to detect UV photons

○ Currently exploring different thin-film photo-conductors which may offer an

• pportunity

○ Exploring amorphous Selenium’s properties

■ Commonly used in X-Ray digital radiography devices

arbitrary units

• If realized, offers a transformative opportunity in LArTPC’s

2 - 10 photons per pixel

Conceptual sketch of device

Incident photons from a 1 GeV muon at 100 cm

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